Rotating assemblies are known in the art for use in high, as opposed to ultra high, vacuum environments. Rotating systems typically include a plurality of crucibles formed in a circular array in the top of a rotating hearth. The rotating hearth sequentially moves the crucibles to a target area where, for instance, an electron beam from an emitter mechanism vaporizes a material in the crucible for thin film deposition on a substrate.
Rotating crucible assemblies typically require a fluid delivery system to supply coolant to water channels formed in the crucible assembly. Prior art fluid delivery systems for rotating apparatus in high vacuum environments generally utilize a rotating apparatus with seals made from elastomeric substances or magnetic fluids placed at the coupling locations to maintain the pressure differential between the ambient coolant supply and the high vacuum environment of the operating apparatus. The elastomeric materials and magnetic fluids provide flexible seals capable of withstanding torsion produced at the coupling locations from rotation of the hearth.
UHV environments, for example those used in physical vapor thin film deposition processes and fabrication processes of integrated circuit semiconductors, require exposure of the assemblies to high temperatures. The elastomeric substances and magnetic fluids used as seals in high vacuum environments cannot be used in an UHV environment for several reasons. First, such substances will not secure an UHV environment; and second, such substances will not withstand high temperatures. UHV environments require all metal sealed fluid delivery systems to prevent outgassing.
All metal sealed fluid delivery systems for UHV environments are known in the art. Such systems typically use a welded bellows with metallic compression seals, and the crucibles are arranged in a linear array because the metal seals cannot withstand torsion produced by rotation. For thin film deposition, for example, the crucibles are sequentially moved past the emitter mechanism using a lengthy, all metal welded bellows assembly. Linear assemblies are typically larger and more cumbersome than the preferred rotating arrangement used in high vacuum environments.
Applicants' co-pending U.S. patent application Ser. No. 07/972,131 discussed a novel UHV, all metal sealed, rotating fluid delivery system for supplying fluid to a rotating assembly operated in an UHV environment. The preferred embodiment utilized an inlet and an outlet bellows coiling together and uncoiling together, in the same plane, in response to rotation of the crucible.
In aspects of the present invention, torque is reduced at the rotating crucible by oppositely winding the inlet and the outlet bellows so that, as the crucible rotates, one bellows uncoils as the other bellows coils. In other aspects of the present invention, a co-axially mounted inlet and outlet bellows pair coils and uncoils in the same direction.